Myocardial Flow Reserve, an Independent Prognostic Marker of All-Cause Mortality Assessed by 82 Rb PET Myocardial Perfusion Imaging: A Danish Multicenter Study

Abstract

BACKGROUND: Rubidium-82 positron emission tomography ( 82 Rb PET) myocardial perfusion imaging is used in clinical practice to quantify regional perfusion defects. Additionally, 82 Rb PET provides a measure of absolute myocardial flow reserve (MFR), describing the vasculature state of health. We assessed whether 82 Rb PET-derived MFR is associated with all-cause mortality independently of the extent of perfusion defects. METHODS: We conducted a multicenter clinical registry-based study of patients undergoing 82 Rb PET myocardial perfusion imaging on suspicion of chronic coronary syndromes. Patients were followed up in national registries for the primary outcome of all-cause mortality. Global MFR ≤2 was considered reduced. RESULTS: Among 7169 patients studied, 38.1% were women, the median age was 69 (IQR, 61–76) years, and 39.0% had MFR ≤2. A total of 667 (9.3%) patients died during a median follow-up of 3.1 (IQR, 2.6–4.0) years, more in patients with MFR ≤2 versus MFR >2 (15.7% versus 5.2%; P <0.001). MFR ≤2 was associated with all-cause mortality across subgroups defined by the extent of perfusion defects (all P <0.05). In a Cox survival regression model adjusting for sex, age, comorbidities, kidney function, left ventricular ejection fraction, and perfusion defects, MFR ≤2 was a robust predictor of mortality with a hazard ratio of 1.62 (95% CI, 1.31–2.02; P <0.001). Among patients with no reversible perfusion defects (n=3101), MFR ≤2 remained strongly associated with mortality (hazard ratio, 1.86 [95% CI, 1.26–2.73]; P <0.01). The prognostic value of impaired MFR was similar for cardiac and noncardiac death. CONCLUSIONS: MFR ≤2 predicts all-cause mortality independently of the extent of perfusion defects. Our results support the inclusion of MFR when assessing the prognosis of patients suspected of chronic coronary syndromes.